diff options
Diffstat (limited to 'arch/arm64/include/asm/nospec-branch.h')
| -rw-r--r-- | arch/arm64/include/asm/nospec-branch.h | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/nospec-branch.h b/arch/arm64/include/asm/nospec-branch.h index 63db0e2b19a2..8a5d2c41da3b 100644 --- a/arch/arm64/include/asm/nospec-branch.h +++ b/arch/arm64/include/asm/nospec-branch.h @@ -8,6 +8,17 @@ #ifdef __ASSEMBLY__ +/* + * On certain processors the bl/ret sequence is a synchronization + * point for any pending speculation, and the value of all registers is + * known after this sequence. So the next flow of instructions, in particular + * any indirect branch, will be executed without any speculation. + * + * This property allows to create the retpoline-like code sequence below. + * Note, that this sequence does not jump to a provided target using the ret + * instruction, instead the ret instruction just goes on and + * the execution sequence continues on the same flow. + */ .macro retpoline alternative_if ARM64_RETPOLINE str x30, [sp, #-16]! |